As U.S. forces begin the planned surge into Afghanistan, we are again reminded that in many ways this is a tougher fight than the military experienced in Iraq. The geography of Afghanistan is daunting, with high mountains, vast deserts and extremes of temperature.

Despite the investment of billions of dollars on infrastructure projects, there are still few roads and only a handful of modern airfields. Despite spending tens of billions of dollars on thousands of Mine Resistant Ambush Protected (MRAP) vehicles for Iraq, the U.S. military was forced to ask the defense industry to design a new protected vehicle, to be built by Oshkosh, suitable for the difficult terrain in Afghanistan.

Similar challenges confront air forces operating over Afghanistan. The lack of roads means that most supplies delivered to our troops must be carried by aircraft. The ordinary wear and tear on aircraft is exacerbated by the environment. Afghanistan’s mountain peaks reach heights of over 20,000 feet. Much of the rest of the country consists of high plateaus or flat deserts, each with extremes of cold and heat. The country only has three truly modern airfields.

Coalition forces have found the environment extremely challenging to air operations. The high mountain range, high temperatures and high runway elevations create a need for greater power and operating capabilities for aircraft flying in this environment relative to Iraq. The higher the temperature and the higher the runway altitude above sea level, the longer the runway needed to gain the speeds needed to take off. The aircraft’s maximum altitude is also affected by these conditions. Once in the air, propeller-driven aircraft are often limited to altitudes under 30,000 feet. This could be a problem of significance for the U.S. Air Force as it considers acquiring a fleet of specialized propeller-driven counterinsurgency aircraft.

In Iraq, it has been possible to provide the new indigenous Air Force with a light strike capability based on a commercial, propeller-driven, air frame. The same option may not work so well in Afghanistan.

Take as an example the effort to create an Air Corps for the Afghan National Army. There are the problems noted above of altitude, terrain and temperature. In addition, airfields vary greatly with runway surfaces ranging from hard-packed earth or gravel to concrete slabs, and runway lengths can be as short as 3,000 feet. While propeller-driven planes may be a cheap solution, in this instance they may not be operationally the best course.

Ultimately, it is a matter of physics. Altitude and temperature affect air density which, in turn, impacts the aircraft’s performance. The greater the altitude and the higher the temperatures the more difficult it is for a propeller-driven aircraft to operate. There is also the threat posed by shoulder-fired surface-to-air missiles. This could force aircraft flying around Afghanistan’s mountains to operate at extremely high altitudes.

Therefore, whether acquiring aircraft for the new Afghan National Army Air Corps or choosing a new U.S. counterinsurgency fighter, turbo-jets may be better than propellers.